Matter
What state of matter has a definite volume but no definite shape.
Liquid
Energy associated with motion is called ______.
Kinetic energy
Convert:
4.5 kJ → J
4500 J
Which provides the most energy per gram?
Carbohydrates = 4 kcal/g
Protein = 4 kcal/g
Fat = 9 kcal/g
What does q represent in q = mcΔT?
Heat energy
Salt water has the same composition throughout. What kind of mixture is it?
Homogeneous mixture
Water stored behind a dam has what type of energy because of its position?
Potential energy
Convert:
7200 cal → kcal
7.2 kcal
How many Calories are provided by 10 g of carbohydrates?
40 Cal
A substance changes from:
20°C → 45°C
Calculate ΔT.
25°C
Is this a physical or chemical change?
A piece of copper is heated and drawn into a thin wire.
Physical change
What generally happens to particle motion when heat is added to a substance?
Particle motion increases.
Convert:
200 cal → J
836.8 J
A food contains:
5 g protein + 4 g fat
How many Calories come from these nutrients?
56 Cal
Protein: 5 × 4 = 20
Fat: 4 × 9 = 36
A 10.0 g substance has:
c = 2.0 J/g·°C
Its temperature increases by 5.0°C.
Calculate q.
100 J
= (10)(2)(5)
What is the main difference between a pure substance and a mixture?
A pure substance has a fixed composition and contains one type of substance; a mixture contains two or more substances physically combined.
Define specific heat.
The amount of heat required to raise the temperature of 1 g of a substance by 1°C.
Convert:
3.00 kcal → J
12,552 J
3.00 kcal × 1000 cal/kcal × 4.184 J/cal
A snack contains:
15 g carbohydrate
5 g protein
4 g fat
Calculate its total Calories.
116 Cal
Carbs: 15 × 4 = 60
Protein: 5 × 4 = 20
Fat: 4 × 9 = 36
A 20.0 g substance absorbs 400 J of heat and increases in temperature by 10.0°C.
Calculate its specific heat.
(might be helpful to rearrange your equation q = mcΔT)
2.00 J/g·°C
c = q/(mΔT)
= 400/(20 × 10)
A student heats solid ice until it becomes liquid water.
Identify:
1. Initial state of matter
2. Final state of matter
3. Physical or chemical change?
4. What happens to particle movement as energy is added?
1. Solid
2. Liquid
3. Physical change
4. Particle movement increases
Two substances have the same mass and absorb the same amount of heat.
Substance A has a lower specific heat than Substance B.
Which undergoes the larger temperature change, and why?
Substance A, because a substance with a lower specific heat requires less energy to change its temperature.
A student wants to convert 500 J → cal and writes:
500 J × (4.184 J / 1 cal) = 2,092 cal
What is wrong with this problem?
The conversion factor is flipped because J needs to cancel.
Use:
500 J × (1 cal / 4.184 J) = 119.5 cal
A food contains 170 Calories.
It contains:
How many grams of fat does it contain?
10 g fat
First find:
Protein = 40 Cal
Carbs = 40 Cal
170 − 80 = 90 Cal from fat
90 ÷ 9 = 10 g fat
A 50.0 g substance has a specific heat of 0.50 J/g·°C and absorbs 500 J.
Its initial temperature is 20°C.
Find its final temperature.
Tf = 40°C
500 = (50)(0.50)(ΔT)
ΔT = 20°C
Tf − 20 = 20